The United States has new evidence showing that the government of Syria used the nerve gas sarin against its own people, Secretary of State John Kerry said Sunday.

Kerry said on news programs Sunday that the U.S. has received hair and blood samples that have "tested positive for signatures of sarin," a deadly nerve agent first developer in Germany in the 1930s.

"In the last 24 hours, we have learned through samples that were provided to the United States and that have now been tested from first responders in East Damascus, and hair samples and blood samples have tested positive for signatures of sarin," Kerry said on NBC's Meet the Press.

On CNN's State of the Union, Kerry laid out the same case, and noted that the new evidence came not from United Nations inspectors but from independent channels. Kerry said the new evidence boosts President Obama's call for Congress to approve military action against Syria. "I believe the case for action will get stronger by the day."

The administration continues to avoid saying that there is 100% proof of its case agaisnt Syrian president Bashar Assad.

"We are saying that the high confidence that the intelligence community has expressed and the case that I laid out the other day is growing stronger by the day," Kerry said on NBC. "We know where this attack came from. We know exactly where it went. We know what happened exactly afterwards." USA NOW 5 reasons to love Labor Day | USA NOW video Aug 30, 2013 David Frost, TV interviewer of Nixon, dies Up Next David Frost, TV interviewer of Nixon, dies ? More Stories: Should the U.S. strike Syria? | USA NOW video News | 4 days ago How To Hit The Golf Ball Dead Straight InstantlyGraves Golf Israelis receive new gas masks amid region tension4 days ago Downsizing? 4 Easy Ways to Get Rid of Your Stuff MySilverAge Syrian impact in USA: Gas, stocks News | 4 days ago Stunning Photos Of Celebrities Most Outrageously Luxurious ...Lonny Manziel issued unsportsmanlike flag, criticized on ESPN NCAAF | 21 hours ago Top 10 Athletes Turned Actors of All TimeRant Sports